1. Field of the Invention
The invention relates to a power transmitting mechanism assembly for a lens driving unit, and more particularly, to power transmitting mechanism assembly for a lens driving unit with improved power transmitting efficiency.
2. Description of the Related Art
An optics system including optical elements, such as lenses, include lens driving units for moving lenses. Lens driving units embody zooming function or auto-focusing function by changing relative distances between lenses by moving the lenses.
A lens driving unit may employ a driving unit like a stepping motor. In this case, it is necessary to employ a decelerating gear and a cam for changing rapid rotation of the step motor to linear movement, resulting in problems such as increase in volume of the lens driving unit, complicated structure of the lens driving unit, errors due to backlashes during normal rotation and reverse rotation, power consumption, high current and large heat generation, etc.
Recently, a piezoelectric device, which operates based on piezoelectric effect, is widely applied for moving lenses of an optics system. A very small driving motor may be manufactured by using a piezoelectric device.
However, in a conventional optics system employing a piezoelectric device, power transmitting efficiency for transmitting driving power of the piezoelectric device to a component for moving lenses is very low.
U.S. Pat. No. 5,335,115 discloses a lens moving mechanism for moving lenses. In a power transmitting mechanism assembly used in such a lens moving mechanism, power is transmitted by using friction force generated as a rotating roller and a ring contact each other. Theoretically, it is possible to acquire higher friction force by pressing a roller to a ring with a strong force. However, by doing so, dust may be formed from contacting surfaces of the roller and the ring, durability of the roller and the ring may be deteriorated, and noise and vibration may be generated. Furthermore, if a roller and a ring are assembled to press each other too weak or too hard, operation force of the power transmitting mechanism may be deteriorated.